Thermostat



Sept. 15, 1936 C. H. DEDERICK THERMOSTAT Filed May 11, 1934 I Patented Sept. 15;, 1936 PTEN QFFEQEE actress nmamosmr I Glinton H. Dederlch,

St. Louis, Mo assignor to The Ememon Electric Mfg. Ga,

St. Louis, Mo.,

' a corporation oi Missouri Application May 11, HM, denial No. 725,138

ple in construction, positive in operation and which will break its contacts abruptly to prevent arcing.

Another object of the invention is to provide a device suitable for use in an electric motor, adjacent the windings, and adapted to break the main circuit in case of overheating oi the windings due to overload or the like.

Further objects will be apparent from the following detail description taken in connection with the accompanying drawing, in which- Fig. 1 is an elevation of one form of the device;

Fig. 2 is a view similar to Fig. l. with the switch contacts open;

Fig. 3 is a sectional view on line Fig. 1;

Fig. is a perspective view of a truss member employed in the construction;

mg. 5 is an elevation of a modified form or the device; and

Fig. 615 an elevation of a further modification.

In the embodiment illustrated in Figs. 1 to 3, a curved bimetallic member, l functionally has two curve sections 2 and 3, the first a major section and the last a minor section. This bimetallic element l is composed of two strips of metal,

superimposed upon one another, the metal of the two strips having a substantially difierent coeificient of thermal expansion. It may be constructed, for example, of a. strip of steel and a strip of brass. The major section 2 is spanned by a truss member 4 as a chord of its curve. The member 4 is normally straight longitudinally and curved laterally, as clearly shown in slightly exaggerated form in Figs. 3 and 4. A

The arrangement is such that the truss member 4 will resist a change of form under stress exerted by the bimetallic section 2 until a condition of instability is reached, and then under further stress will abruptly change its form and release the stress exerted by the bimetallic section 2.

It will thus be seen that a contact such as 5 which is mounted on the truss member 4 and movable therewith remains almost stationary during minor temperature changes, but will have a decided deflection when the stress on the bimetallic section 2 is sumcient to cause the abrupt change in position above described.

Notwithstanding the tendency of the assembly just described, which includes the bimetallic section 2 and the truss 4, to resist a change in form,

minor changes in disposition of. the contact will. occur upon a gradual rise of temperature. To

compensate for these, minor changes in position of the contact 5, a cooperating contact 5 is movable by the minor section 3 oi. the bimetallic element 0. The contact 6 is carried on the iree end of an arm i, of nonconductive material,

which is mounted at its one end on and sup= ported by the outer end of the section As the device is subjected to heat, the contact 5 will be slightly depressed, but the contact 6 will be depressed by the section 3 to follow the initial minor movements of the contact 5. But when the stresses in the section 2 have increased to a point as will cause the abrupt change in shape of the truss 4, the contact 5 will be sharply and quickly moved away from the contact 6 and these contacts will thereafter remain separated because of the differences in moments of the sec-= tions 2 and 3.

In the embodiment shown in Fig. 5 the same principles are involved as in the preceding emlib and the truss l is outer ends of the bimetallic member band the truss Li. A cooperating contact i i is carried on the outer end of a minor bimetallic member i2, which has its other end secured to and supported by a horizontal portion 53 of the nonconductive base.

In the embodiment shown in Fig. 5 heating of the device will causea slight rise in the position of the contact I0, but any great change in position is resisted by the truss 4 until a condition of instability is reached, after which further stress will cause an abrupt rise of the contact.

The initial rise in the contact 10 is followed by a rise in the contact H, due to the action of the minor bimetallic member l2.

The embodiment shown in Fig. 6 is constructed substantially like that of Fig. 5, except the curve of the major bimetallic m mber I4 is substantially that of an arc of a circle and the ends of that element lie in the same plane. ported end of the member overhanging arm The sup- N is attached to an IE of a nonconductive base,

which has a horizontal portion It, to which is attached a' minor bimetallic element ii. The contact I0 is carried on the outer end of the major bimetallic member i4 ancLthe contact ii is carried on the end of the minor bimetallic member II. It will be understood that the action of the embodiment shown in Fig. 6 is the same as that described above in connection with that of Fig. 5.

It will be obvious that various changes may be made in the details of the construction, within the scope of the appended claims, without departing from the spirit of this invention.

I claim:

L In a thermostatic switch, a major curved bimetallic member, a resilient truss member connected to saidmajor member as a chordthereof and arranged to resist a change in form under stress exerted by the bimetallic member until a condition of instability is reached, and then under further stress to abruptly change its form and release the stress exerted by the major member, a contact movable by said major bimetallic member, a minor bimetallic member, and a contact movable by the minor bimetallic member and arranged to cooperate with the other contact, said minor bimetallic member being positioned and arranged with respect to the major member in such a manner as to move its contact to compens'ate for initial minor movements of the first contact induced by said major member before the said abrupt change in the truss member.

2. In-a thermostatic switch, a curved major bimetallic element, a resilient truss member connect od to said bimetallic member as a chord thereof and arranged toresist a change of form under stress exerted by the bimetallic member until a condition of instabilityis reached and then, under further stress, to abruptly change its form and release the stress exerted by thebimetallic member, a contact mounted on and carried by said major bimetallic member, a minor bimetallic member, anda contact movable by the bimetallic member and arranged to cooperate with the other contact, said minor bimetallic member being so positioned and arranged with respect to the major bimetallic mem ber as to move its contact to compensate for initial minor movements of the first contact induced by said major member before the said abrupt change in the major member.

3. In a thermostatic switch, a curved major bimetallic element, a resilient truss member connected to said bimetallic member as a chord thereof and arranged to resist a change of form under stress exerted by the bimetallic member until a condition of instability is reached and then, under further stress, to abruptly change its form and release the stress exerted by the bimetallic member, a contact movable by said truss member, a minor bimetallic member, and a contact movable by said minor member and arranged to cooperate with the other contact,

said minor bimetallic member being so positioned and arranged with reference to said major member as to move its contact to compensate for initial minor movements of the first contact induced by'said major member before the said abrupt change in the truss member.

.4. In a thermostatic switch, a curved major bimetallic element, a resilient truss member connected to said bimetallic member as a chord thereof and arranged to resist a change of form under stress exerted by the bimetallic member until a condition of instability is reached and accepts then, under further stress, to abruptly change its form andrelease the stress exerted by the bimetallic member, a contact mounted on and movable by said truss memben'a minor bimetalence to said major member as to move its contact to compensate for initial minor movements -of the first contact induced by said major member before the said abrupt change in the truss member.

5. In a thermostatic switch,'a bimetallic member having a major curved section and a minor curved section, a resilient truss member connected to said major curved section as a chord thereof and arranged to resist a change of form under stress exerted by said major section until a condition of instability is reached and then, under further stress, to abruptly change its form and release the stress exerted by said major section, a contact movable by said major section, a cooperative contact movable by said minor section, said major portion and said curved portion being so arranged with respect to each other that the minor section may move its contact to compensate for initial minor movements of the first contact induced by said major section before the said abrupt change in the truss member.

6. In a thermostatic switch, a bimetallic member having a major curved section and a minor curved section, a resilient truss member connected to said major section as a chord thereof and arranged to resist a change of form under stress exerted by the major section until a condition of instability is reached and then, under further stress, to abruptly change its form and '7. In a thermostatic switch, a major curved bimetallic member fixed at one end to a support, a resilient truss member connected to said himetallic member as a chord thereof and arranged to resist a change of form under stress exerted by the bimetallic member until a condition of instability is reached and then, under further stress, to abruptly change its form and release the stress exerted by the bimetallic member, a contact mounted on and carried by said major member at its free end, a minor bimetallic member fixed at one end to the support and carrying a cooperating contact at its other end, said minor member being so positioned and arranged with respect to said major member as to move its contact to compensate for initial minor movements of the first contact induced by said major member before the said abrupt change in the truss member.

8. In a thermostatic switch, a major bi. metallic member curved laterally and fixed at one end to a support, a resilient truss member connected at one end to the support, secured at its other end to the free end of said major member and arranged to resist a change of form under stress exerted by said major member until a condition of instability is reached and then, un.

der further stress to abruptly change its form and release the stress exerted by said major member, a contact mounted on the free end of said major member, and a minor bimetallic member fixed at one end to the support and carrying a cooperating contact at its other end, said minor member being so positioned and arranged with respect to said major member as to move its contact to compensate for initial minor movements of the first contact induced by said major member before the said abrupt change in the truss member.

9. In a thermostatic switch a curved bimetallic member, a resilient truss member connected to said major member as a chord thereof, a contact movable by said truss member, said truss member being arranged to resist a change in form under stressexerted by the bimetallic member but to move the contact in a minor manner until a condition of instability is reached and then 5 cLm'roN n. nnnnmc'x. 15 

